1. Field of the Invention
The present invention relates to an oxygen enriching apparatus (or oxygen concentrator) capable of producing high-concentration oxygen from, for example, air through adsorption removal of nitrogen from the air and supplying the high-concentration oxygen to, for example, a patient. The present invention further relates to a controller and a recording medium for the oxygen enriching apparatus.
2. Description of the Related Art
Conventionally, an oxygen enriching apparatus for medical use capable of producing an oxygen-enriched gas from, for example, air through adsorption removal of nitrogen from the air and supplying high-concentration oxygen to a patient has been used in, for example, home care oxygen therapy.
Since a patient who uses such an oxygen enriching apparatus is weak in lung function as compared with healthy persons, the patient must use the oxygen enriching apparatus all day long. Therefore, an oxygen enriching apparatus which can be used conveniently for daily living has been in demand.
When the condition of the patient is good, the flow rate of the oxygen-enriched gas (hereinafter also referred to as “oxygen flow rate”) is typically set to 2 liters/min or less (hereinafter “min” may be omitted), and this flow rate is sufficient. However, when the condition of the patient becomes worse, an oxygen flow rate of greater than 2 liters/min is required, and in order to provide a margin for safety, an oxygen flow rate of about 5 to 7 liters/min is required.
3. Problems Solved by the Invention
When the capacity of the oxygen enriching apparatus is increased, the oxygen-enriched gas can be supplied at a higher flow rate. However, in such a case, the size of the oxygen enriching apparatus increases, raising the following problems (1) to (3).
(1) Since the volume and weight of the oxygen enriching apparatus increase, a large burden is imposed on a caregiver when he or she transports or moves the oxygen enriching apparatus.
In an example case in which a caregiver or a sales representative transports the oxygen enriching apparatus to the patient's house and installs it there, the caregiver or sales representative cannot perform the installation work by himself because of the large size of the apparatus, and the caregiver or sales representative must bear a considerably large burden.
(2) Due to increased consumption of electrical power, there is a resultant increase in cost.
For example, the electrical-power consumption of an oxygen enriching apparatus having a capacity of 5 to 7 liters/min (5 to 7 liter model) (450W) is about two times that of a conventional 2 liter or 3 liter model.
(3) Increased noise hinders good sleep of the patient. When a measure for the noise is employed, the volume and weight of the oxygen enriching apparatus increase further.
For example, if a soundproofing material is disposed as a measure against noise during operation, the volume and weight of the oxygen enriching apparatus increase further, and the increased weight (45 Kg) is about two times that of the conventional 2 liter or 3 liter model. However, in spite of provision of the soundproofing material, the noise level is still high, thus failing to guarantee that the patient will sleep well.
That is, conventional oxygen enriching apparatus for medical use and ordinary oxygen enriching apparatus are based on the same design concept. Therefore, when oxygen is to be supplied at a flow rate of 5 liters/min, the capacity of a compressor and the amount of an adsorbing material for adsorbing nitrogen must be increased, and an electromagnetic valve of a larger diameter suitable for the increased flow rate must be used as an electromagnetic valve for controlling the feeding of compressed air from the compressor to the adsorbing material. Consequently, the sizes of components naturally increase, and the above-described problems (1) to (3) arise.
Apart from the above-described technique regarding oxygen enriching apparatus, a technique has been developed in which a patient carries an oxygen cylinder with him or her during travel or at the time of visiting a hospital.
In this technique, a breath synchronizer for supplying oxygen synchronously with breathing is used so as to reduce consumption of oxygen supplied from the cylinder, to thereby extend the service life of the oxygen cylinder.
The breath synchronizer utilizes the rule of thumb that in the case of a human the ratio between the inhalation period and the exhalation period is 1:2. Upon detection of inhalation by means of a sensor, the breath synchronizer supplies high-concentration oxygen from the oxygen cylinder over a short period of time (in the manner of a pulse).
The technique can reduce the consumption of oxygen stored in the oxygen cylinder and the consumption of drive batteries, because high-pressure oxygen is supplied from the oxygen cylinder only for a short period of time upon start of inhalation. However, the technique involves another problem in that the patient feels that something is wrong, because the breath synchronizer creates a breathing condition that differs from ordinary breathing condition.
In recent years, a technique for applying the breath synchronization technique used with an oxygen cylinder to an oxygen enriching apparatus has been proposed (see, for example, Japanese Patent Application Laid-Open (kokai) No. 8-187289). However, effective ways for solving the above-described problems caused by the increased apparatus size have hardly been studied.